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/lib/pods/SDL/Cookbook/PDL.pod

http://github.com/PerlGameDev/SDL
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 1
 2=pod
 3
 4=head1 NAME
 5
 6SDL::CookBook::PDL -- CookBook for SDL + PDL
 7
 8PDL provides great number crunching capabilities to Perl and SDL provides game-developer quality real-time bitmapping and sound.  You can use PDL and SDL ''together'' to create real-time, responsive animations and simulations.  In this section we will go through the pleasures and pitfalls of working with both powerhouse libraries.
 9
10
11=head2 CATEGORY
12
13Cookbook
14
15=head1 Creating a SDL Surface piddle
16
17PDL's core type is a piddle. Once a piddle is provided to PDL it can go do a numerous amounts of things. Please see the example in 'examples/cookbook/pdl.pl' that came with this module.
18
19=head2 Creating a simple piddle
20
21First lets get the right modules.
22
23  use PDL;
24  use SDL::Rect;
25  use SDL::Video;
26  use SDL::Surface;
27  use SDL::PixelFormat;
28
29Suppose you want a surface of size (200,400) and 32 bit (RGBA).
30
31   my ( $bytes_per_pixel, $width, $height ) = ( 4, 200, 400 );
32
33Define the $width, $height and $bytes_per_pixel. Your $bytes_per_pixel is the number of bits (in this case 32) divided by 8 bits per byte. Therefore for our 32 bpp we have 4 Bpp;
34
35   my $piddle  = zeros( byte, $bytes_per_pixel, $width, $height );
36
37Create a normal $piddle with zeros, byte format and the Bpp x width x height dimensions.
38
39   my $pointer = $piddle->get_dataref();
40
41Here is where we get the actual data the piddle is pointing to. We will have SDL create a new surface from this function.
42
43   my $surface = SDL::Surface->new_from( $pointer, $width, $height, 32,
44        $width * $bytes_per_pixel );
45
46Using the same dimensions we create the surface using new_form. The width *  Bpp is the scanline (pitch) of the surface in bytes.
47
48   warn "Made surface of $width, $height and ". $surface->format->BytesPerPixel;
49   return ( $piddle, $surface );
50
51Finally make sure that the surface actually has the correct dimensions we gave.
52
53B<NOTE:> $surface->format->BytesPerPixel must return 1,2,3,4. !!
54
55Now you can blit and use the surface as needed; and do PDL operations as required.
56
57
58=head2 Operating on the Surface safely
59
60To make sure SDL is in sync with the data. You must call SDL::Video::lock B<before> doing PDL operations on the piddle.
61
62    SDL::Video::lock_surface($surface);
63
64    $piddle->mslice( 'X', [ rand(400), rand(400), 1 ], [ rand(200), rand(200), 1 ] )
65        .= pdl( rand(225), rand(225), rand(255), 255 );
66
67After that you can unlock the surface to blit.
68
69    SDL::Video::unlock_surface($surface);
70
71=head2 Error due to BPP at blitting
72
73When blitting the new surface check for the return value to see if there has been a problem.
74
75    my $b = SDL::Video::blit_surface(
76        $surface,  SDL::Rect->new( 0, 0, $surface->w, $surface->h ),
77        $app, SDL::Rect->new(  ( $app->w - $surface->w ) / 2, ( $app->h - $surface->h ) / 2, $app->w, $app->h )
78       );
79
80    die "Could not blit: " . SDL::get_error() if ( $b == -1 );
81
82If the error message is 'Blit combination not supported' that means that the BPP is incorrect or inconsistent with the dimensions.
83After that a simple update_rect will so your new surface on the screen.
84
85=head1 AUTHORS
86
87See L<SDL/AUTHORS>.
88
89
90=cut